This is company's third tranche of planned Rs 10,000 crore fund raise it had announced in June this year.
"In terms of the board authorisation..The company has today alloted its third tranche of secured, redeemable, non- convertible debentures aggregating to Rs 850 crore," an exchange filing of the company said.
Available with four options, the bonds carry coupon rate in range of 7.40-7.82 per cent.
Shares of the company closed 3.77 per cent up at Rs 1,198.75 on BSE.